The '''National Institutes of Health''' ('''NIH''') is a biomedical research facility primarily located in Bethesda, Maryland
. An agency of the United States Department of Health and Human Services
, it is the primary agency of the United States government responsible for biomedical
and health-related research. The NIH both conducts its own scientific research through its NIH Intramural Research Program|Intramural Research Program
(IRP) and provides major biomedical research funding to non-NIH research facilities through its Extramural Research Program.
With 1,200 principal investigator
s and more than 4,000 postdoctoral
fellows in basic, translational, and clinical research, the IRP is the largest biomedical research institution in the world,
while, as of 2003, the extramural arm provided 28% of biomedical research funding spent annually in the U.S., or about US$26.4 billion.